From European patent EP-A-0 472 361 is notably known a portable workstation comprising a personal computer and a mobile telephone in one and the same construction. This device comprises a pivoting keyboard part that enables to change from a mobile telephone keyboard to a keyboard of a personal computer, which change is accompanied with the change from a small display to a large display. During this movement, however, the size of the device is notably increased and the keys of the mobile telephone keyboard remain accessible, not protected, and may be operated inadvertently.